Evaluation of the safety and efficacy of pathotropic nanoparticles bearing a dominant negative cyclin G1 construct for chemoresistant osteosarcoma and other sarcomas: Phase I, II, and III studies
10513 Background: (1) To evaluate the safety/anti-tumor potential of intravenous (i.v.) Rexin-G in chemotherapy-resistant sarcoma (Phase I/II), and (2) to confirm the efficacy/safety of i.v. Rexin-G in chemotherapy-resistant osteosarcoma (Phase II). Methods: Twenty patients in the Phase I/II study and 22 patients in the Phase II study received 1–2 × 10e11 cfu Rexin-G i.v., 2–3 times a week for 4 weeks. Treatment was continued if the patient had < Grade 1 toxicity. Results: Treatment-related adverse events included chills (n=1), presyncope (n=1), photophobia (n=1) of Grade 1 severity, and fatigue (n=4) of Grade 1–2 severity. In the Phase I/II sarcoma study, 3/6 patients had stable disease at Dose Level 0, median progression free survival (PFS) was 5 weeks, and overall survival (OS) was 14 weeks, while 10/14 patients had stable disease at Dose Level I-II, median PFS was 16 weeks and median OS was 34 weeks. Cox regression analysis showed a dose-response relationship between PFS/OS and Rexin-G dosage (p = 0.02 and 0.005, respectively). The Table below shows the results for evaluable patients (n=17) in the Phase II study for osteosarcoma. Kaplan-Meier analysis shows a dose-response relationship between overall survival and Rexin-G dosage in the combined Phase I/II sarcoma and Phase II osteosarcoma studies (p = 0.02; n=42). Two patients achieved surgical remissions which are sustained for >26 weeks. Conclusions: These studies suggest that (i) intravenous Rexin-G is safe and well-tolerated, and (ii) Rexin-G controls tumor growth and prolongs progression-free survival and overall survival in a dose-dependent manner in chemotherapy-resistant osteosarcoma and sarcoma. [Table: see text] [Table: see text]